Reversible two-stroke cycle internal combustion engine



Aug. 16, 1955 F. LEHNER 2,715,393

REVERSIBLE TWO-STROKE CYCLE INTERNAL COMBUSTION ENGINE Filed June 4, 1953 3 Sheets-Sheet l I N VEN TOR.

Aug. 16, 1955 F. LEHNER 2,715,393

REVERSIBLE TWO-STROKE CYCLE INTERNAL COMBUSTION ENGINE Filed June 4, 1955 3 Sheets-Sheet 2 IN VEN TOR.

F. LEHNER Aug. 16, 1955 REVERSIBLE TWO-STROKE CYCLE INTERNAL COMBUSTION ENGINE 3 Sheets-Sheet 5 Filed June 4, 1953 INVENTOR.

United States Patent Ufifice 2,715,393 Patented Aug. 16, 1955 REVERSIBLE TWO-STROKE (IYCLE INTERNAL CONIBUSTION ENGINE Felix Lehn'er, Hallain, Saizburg, Austria, assignor to Hans List, Graz, Austria Application June 4, 1953, Serial No. 359,488

11 Claims. (Cl. 123-41) The invention relates to a process and apparatus for reversing the direction of rotation of internal-combustion engines.

It is known that for reversing the direction of rotation of valve-controlled internal-combustion engines with fuel injection the valve timing, the time of injection and in some cases also the time of ignition must be approximately symmetrical with respect to the inner dead centre position of the working piston of the engine. Usually this is effected by a corresponding change in the drive of the means for changing the charge, as well as of the pumps and starting devices.

In four-stroke combustion engines for this purpose the camshaft is displaced either directly by hand or indirectly by means of compressed air or pressure oil to cause the engagement of a second set of cams. larly compressed-air operated reversing devices are provided with devices, e. g. oil brakes, for damping the reversing piston. It is also known to effect the displacement of the camshaft automatically by a control piston, the head ends of which communicate by conduits with the pressure and suction sides, respectively, of the lubricating oil pump of the engine. In altering the direction of rotation the pressure and suction spaces of the lubricating oil pump are reversed, whereby a displacement of the control piston and a consequent displacement of the camshaft is effected.

In two-stroke engines having piston-controlled admission and exhaust ports the reversal of the direction of rotation is simpler because in this case any measures regarding the timing of the admission and exhaust are eliminated. If, however, the engine has also an exhaust rotary slide valve for closing the exhaust channels while or before the admission ports are covered by the working piston, that type of machine also requires a change in timing.

It is known to provide drag coupling in the gear of the auxiliary devices, such as starting rotary slide valve and injection pumps, which couplings like claw coupling have claw-type coupling members which can assume two positions of engagement, offset by the required angle, in dependence of the direction of rotation.

The application of drag couplings which eliminates the expensive separate cams for the forward and reverse operation and the appertaining shifting device has also various disadvantages. Contact pressure is required for the accurate engagement of the claws in the respective position of engagement. This contact pressure is, however, present only when power is being transmitted from the engine to the respective device by the drag coupling. If this is not the case, e. g. when the engine is at rest or delayed or when the conditions of friction are changed, the relative position of the claws of the drag coupling is undetermined or may correspond even to the position associated with the operation in the opposite sense. Thereby disturbances in starting and during operation as well as damages of the engine may occur.

In known reversing devices the disadvantages appearing Particu- J v operation.

during operation of the engine are avoided thereby that each of the drag couplings has a rotary piston with two positions of engagement, the two end positions of the rotary pistons corresponding to the forward and reverse operation, respectively, of the engine. The reversal of the rotary pistons is effected by pressure oil supplied from a special source into the pressure spaces arranged at both sides of the rotary pistons. By that measure the rotary pistons of the drag couplings are retained by force in their respective position of engagement whether or not power is being transmitted to the device through the drag coupling.

in order to eliminate the expensive special source of pressure oil, which source is always to be operated with the engine, in another device for the, reversal of the direction of rotation it has been suggested to remove the pressure oil from the lubrication system of the internalcombustion engine. in this case, however, the disadvantage ensues that whenever no pressureor no. sufiicient pressure is available in the lubrication system of the engine, that is, before and during starting, no reversal will be possible.

According to the invention these disadvantages of the known reversing devices are avoided in reversing the rotary pistons by the admission of compressed air and retention duringoperation by means of pressure oil from the circulating lubrication system of the engine, This enables, on the one :hand, the reversal to be efiected at any time, even when the engine is at rest, and, on the other hand, the accurate retention of the rotary piston duringoperation is ensured by pressure oil without requiring a separate source of pressure oil during operation. During the reversal by compressed air the oil on the side of the rotary piston where no compressed air is admitted causes a damping of the reversing operation.

According to another reature ofthe invention the-compressed air serving to start the engine is used for the reversal of the rotary piston and admitted to the rotary piston and starting valves through .a common control element. This provides fora simplification .in the control mechanism and ensures, in any case, that when starting the engine it has been reversed infactio the desired direction of rotation.

In order to provide for a most simple operation the invention furthermore suggests to control and operate the pressure oil from the circulating lubrication system of the engine for retaining "the rotary pistons in their positions of engagement and the common element :for controlling the compressed air for starting the engine 'and reversing the rotary pistons, as well as the -.connection of the spaces behind that sidesof the rotary-pistons which are not pressed by .a medium and the router air by a single control roller, which is directly or indirectly connected with the control lever.

For the completion .of the operation -with ,a single control lever, it is moreover suggested to efiect-byacam on the control roller also the axial displacement of the group'of cams known per se and rotating :with crankshaft speed andby which control slide valves are operated each of which is associated with one cylinder and cyclically admits compressed airto and subsequently air-relieves an actuating piston for the appertaining starting valve, and which group comprises cams for forward and reverse According to a further feature of the invention another cam on the control cylinder is effective in setting the control rod of .the injection pump to zero delivery in the positions step, ahead starting? or back starting and in releasing the rod in the operating positions. 4

Hereinafter the invention is illustrated by an example. Fig. 1 is an axial section of a drag coupling,

Fig. 2 is an appertaining cross-section along the line H-II of Fig. 1.

Figs. 3 to 7 show schematically a reversing device in the various positions of the control lever stop, ahead starting, ahead running, back starting and back running for a four-cylinder two-stroke engine. The drag coupling (Figs. 1 and 2) connecting the shafts '1 and 2 from which one is the driving, the other the driven shaft, has a rotary piston 3 fixed with the shaft '1 to a cone 4 by a key 5 and secured against rotation by'a bushing 6 and a screw 7. The shaft 1 is mounted in a bearing body 8, the-internal space of which is sealed from the cylindrical part of the rotary piston 3 by a felt ring '9 or the like. Between the bearings 10 and the rotary'piston 3 spacers 11 are arranged, the thickness of which can be varied if desired. The rotary piston 3 is arranged with its free end having a segment-shaped cut-out portion 29 in a casing 12 firmly connected to the shaft 2. On one side the casing 12 has at 13 a slot in which the radially inwardly protruding abutment 14 is arranged and clamped fastly by means of three screws 15. As may be seen from Fig. 2, the rotary piston 3 can rotate relatively to the abutment 14 by a certain angle and in the end positions is in full contact with one of its two longitudinal surfaces 16 or 17 on the abutment '14. Each of the longitudinal surfaces 16 and 17 of the rotary piston 3 has an undercut portion 18 and 19, respec- 23 and 24, respectively, in the shaft 1 with annular grooves 25 and 26, respectively of the bearing 10 which lead outwardly through the bores 27 and 28, respectively.

When pressure medium is supplied through one of the bores 27 and 28 and at the same time the second bore 1 is air-relieved the rotary piston 3 will turn to one side or the other relatively to the casing 12 until it engages with the abutment 14. The angle at the centre of the segment-shaped cut-out portion 29 determines the possible angle through which the rotary piston 3 and the shaft 1 can be rotated relatively to the casing 12 and the shaft '2, respectively.

Figs. 3 to 7 diagrammatically show the total arrangerhent of the reversing device by using the drag coupling mentioned-above for the five characteristic positions of the control lever.

' The four-cylinder two-stroke engine is indicated by the cylinder 30, the piston 31, the connecting rod 32, and

1 crankshaft 33. 34 designates the admission and 35 the exhaust port. In the exhaust line leading to the exhaust manifold 37 an exhaust rotary slide valve 38' isarranged driven with crankshaft speed from the crankshaft 33 by means of toothed wheels 39, 40 and 41, the shaft 2, the drag coupling 3', 12' and the shaft 42. The shaft 2 drivesthe shaft 1 of the fuel injection pump 43 through a second drag coupling 3, 12.

The control cylinder 44 rotatable'by the control lever 45- serves for controlling the engine. The control cylinder 44 controls for the forward and reverse operation the admission of pressure oil from the circulating lubrication system of the engine to the two drag couplings 3, 12 and 3', 12', as well as the starting operation; moreover, the control rod 46 of the fuel injection pump 43 is forced into' position for Zero delivery by means of a cam 68 and a rod 69, if necessary. The starting operation is controlled by a cam 47, which is arranged on the control cylinder 44 and can open the controlling air valve 48 against the force of the spring 49, and by a second cam 50 which through a linkage 51 and a twoarmed lever 52 operates the group of earns 53 axially displaceable on the shaft 2 but connected for rotation therewith. The. group of cams 53 having a separate cam for the forward and reverse operation of each cylinder possesses atthe right-hand end a circular groove 54into which engagesthe two-armed lever 52. In accordance with the number of cylinders four control slide valves 56 are arranged over the group of cams 53. Each of said slide valves 56 is urged off the cams by a spring 55. One of the slide valves 56 is shown in Figs. 3 to 7, whereas the position of the other slide valves is merely indicated.

For starting the engine compressed air from the container 57 and the line 53 is passed through the controlling air valve 48 into the space 59; the main starting valve 60 is opened by way of the line 61 by an auxiliary piston 63 loaded by a spring 62. At the same time the control slide valve 56 opens in the stroke of the engine the starting valve 65 in the cylinder head by compressed air through the line 64 and the auxiliary piston 67 loaded by a spring 66. From the space 59 compressed air is also talent for admission to the rotary piston 3 and 3' in the drag couplings and is passed to line 27 or 28 by the control cylinder 44 in dependence on the direcnon of rotation. The respective free line 28 and 27, respectively, is connected to the atmosphere, also through the control cylinder 44. v

During operation of the engine the admission of the rotary pistons 3, 3' is effected instead of with compressed air with pressure oil supplied from the lubrication system through the line 7 9 and controlled also by the control cylinder 44. The oil thus entering the drag couplings and control lines at the same time causes the necessary damping of the rotary piston movement when the reversal is effected with compressed air.

Hereinafter the controlling operations in the live control positions stop, ahead starting, ahead running, back starting and back running will be explained with reference to the diagrams of Figs. 3 to 7. For better understanding the lines leading compressed air are marked uniformly with dots, the air-relieved lines communicating with the atmosphere are left free and the oil conducting lines are marked with dashes.

in the stop position of the control lever 45 and control cylinder 44 (Fig. 3) the controlling air valve 48 is closed, the space 59 is air-relieved and the control slide valves 56 are lifted from the group of cams. For this reason, line 64 is connected through the opening 71 with the atmosphere and the starting valve 65 is closed. The spaces at both sides of the rotary piston 3, 3 are airrelieved through the lines 2'7, 28, the control cylinder 7 44 and the line 72. The control rod 46 of the fuel injection pump 43 is pressed to zero delivery position by the cam 68.

In the control position ahead starting (Fig. 4) the controlling air valve 48 is pressed open by the cam 47. The space 59 is under air pressure and therefore the main starting valve 60 opened. The control valve 56 is forced 7 against the force of the spring 55 to the front face of the cam by the pressure and connects the line 64 in the stroke of the'engine alternatively with the pressure space 59 and then through the opening 71 with the atmosphere. The two rotary pistons 3 and 3 are at one side supplied with pressure air from the space. 59 through the line 27 and the connecting line 73 in the control cylinder 44 and are thus retained in the fforward position which corresponds to the sense of rotation of the engine as indicated by arrows. The other sides of the rotary pistons cornrnunicate with the atmosphere through the line 28, t e control cylinder and the line 72. The control rod 46 of the fuel injection pump 43 is pressed into the Zero delivery position by the cam 68.

In the control position fahead running (Fig. 5) of the control lever the controlling air valve 48, the main starting valve 60, and the starting valve 65 areclosed. The control slide valve 56 is lifted from the group of cams 53. Those sides of the rotary pistons 3, 3' which are connected with pressed air during ahead starting (Fig. 3) are now communicated with the pressure lubrication system of the engine through the lineand channel 74 in the control cylinder 44. The rear sides of the rotary pistons again communicate with the atmosphere through the lines 28 and 72. The control rod 46 of the fuel injection pump 43 is released by the cam 68 and the rod 69.

The control position back starting (Fig. 6) differs from the control position ahead starting (Fig. 4) only therein that corresponding to the reversed sense of rotation of the engine, indicated also by arrows, the group of cams 53 has been displaced to the right in the drawing by the cam 50 so that the control slide valves 56 engage the reverse-operation cams. Moreover, the rotary pistons 3, 3' engage again the casing 12, 12 at that side which corresponds to the drag position for the altered sense of rotation. This is effected by connecting the pressure space 59 through the bore 75 in the control cylinder 44 with the line 28. The other sides of the rotary pistons 3, 3' communicate with the atmosphere through the lines 27 and 72.

The control position back running (Fig. 7) also differs from that for ahead running (Fig. 5) only by the posi tion of the group of earns 53 and by the fact that in the present case the line 27 carries pressure oil whereas the line 28 is air-relieved. This connection of lines is effected by the connecting lines 76 and 77 in the control cylinder 44.

What I claim is:

1. In a reversible internal combustion engine the combination comprising a crankshaft, an injection pump driven by the crankshaft through gearing, a drag coupling between the gearing and injection pump, and including a rotary piston and cylinder therefor, the piston having two sides each engageable by a fluid and rotated thereby in a direction depending on the piston side engaged by the fluid to either of two positions, two fluid supply lines, one supplying fluid to one side of the piston and the other to the other side of the piston, and both connected to the atmosphere, a reservoir supplying compressed air, a control device selectively movable from stop position for starting the engine to either of two positions each stopping the delivery of the injection pump, and each connecing one of the supply lines to the reservoir and the other to the atmosphere, a circulating lubrication ssytem, the control device being also selectively movable from stop position for running the engine to either of two other positions each connecting one of the supply lines to the circulating lubrication system and the other to the atmos phere.

2. The combination according to claim 1 and wherein the engine is of the two-cycle type.

3. The combination according to claim 1' and also comprising an exhaust rotary slide valve driven by the crankshaft through gearing, a drag coupling between the gearing and exhaust valve and including a second rotary piston and cylinder therefor, the piston having two sides engageable by a fluid and rotated thereby in a direction determined by the piston side engaged by the fluid to either of two positions, one of the two supply lines supplying fluid to one side of the piston of the exhaust valve and the other line supplying fluid to the other piston side.

4. The combination according to claim 3 and wherein the drag coupling piston has a segmental cut-out and the drag coupling cylinder carries an abutment radially extending into the cut-out and dividing same into two operating chambers and also comprising a journal for the piston with an annular space communicating with the control device through which alternately compressed air or lubricant is conducted and through which one of the supply lines is connected to the atmosphere.

5. The combination according to claim 3 and wherein the engine is of the two-cycle type.

6. The combination according to claim 5 and also comprising cylinders, pneumatic means for starting the engine and including starting valves each controlling the admission of air from the reservoir into a cylinder and a control element controlling the supply line carrying compressed air and controlling the starting valves.

7. The combination according to claim 6 and wherein the operation of the control element and the communication of the piston sides not engaged by fluid pressure with the atmosphere is effected by a single control cylinder of the control device.

8. The combination according to claim 6 and wherein the starting valves are controlled by compressed air and cam means driven by the crankshaft and control slide valves are provided, each controlled by a cam and controlling an auxiliary piston for each starting valve, the cam means comprising two cams for each cylinder, one for forward operation and one for backward operation and being axially displaced by the control device.

9. The combination according to claim 6 and wherein the injection pump has a control rod set to Zero delivery position by the control device in the stop position and starting positions.

10. In a reversible internal combustion engine the combination comprising a crankshaft, an exhaust rotary slide valve driven by the crankshaft through gearing, a drag coupling between the gearing and exhaust valve and including a drag piston and cylinder therefor, the piston having two sides each engageable by a fluid and rotated thereby in a direction depending on the side engaged by the fluid, two fluid supply lines one supplying fluid to one side of the piston and the other to the other piston side, a reservoir supplying compressed air, a control device selectively movable from stop position for starting the engine to either of two positions determining the direction of operation of the exhaust valve and connecting one of the supply lines to the reservoir and the other to the atmosphere, a circulating lubrication system, the control device being also selectively movable from stop position to either of two other positions each connecting one of the supply lines to the circulating lubrication system and the other to the atmosphere.

11. The combination according to claim 10 and wherein the engine is of the two-cycle type.

References Cited in the file of this patent UNITED STATES PATENTS 

